Other Conditions

Amblyopia is a term used to describe an uncorrectable loss of vision in an eye that appears to be normal. It’s commonly referred to as “lazy eye” and can occur for a variety of reasons.

A child’s visual system is fully developed between approximately the ages of 9-11. Until then, children readily adapt to visual problems by suppressing or blocking out the image. If caught early, the problem can often be corrected and the vision preserved. However, after about age 11, it is difficult if not impossible to train the brain to use the eye normally.

Some causes of amblyopia include: strabismus (crossed or turned eye), congenital cataracts, cloudy cornea, droopy eyelid, unequal vision and uncorrected nearsightedness, farsightedness or astigmatism. Amblyopia may occur in various degrees depending on the severity of the underlying problem. Some patients just experience a partial loss; others are only able to recognise motion.

Patients with amblyopia lack binocular vision, or stereopsis – the ability to blend the images of both eyes together. Stereopsis is what allows us to appreciate depth. Without it, the ability to judge distance is impaired.

Nearsightedness or myopia occurs when light entering the eye focuses in front of the retina instead of directly on it. This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye. Near-sighted people typically see well up close, but have difficulty seeing far away.

This problem is often discovered in school-age children who report having trouble seeing the chalkboard. Near-sightedness usually becomes progressively worse through adolescence and stabilises in early adulthood. It is an inherited problem.

Farsightedness or Hyperopia occurs when light entering the eye focuses behind the retina, instead of directly on it. This is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye. Farsighted people usually have trouble seeing up close, but may also have difficulty seeing far away as well.

Young people with mild to moderate hyperopia are often able to see clearly because their natural lens can adjust, or accommodate to increase the eye’s focusing ability. However, as the eye gradually loses the ability to accommodate (beginning at about 40 years of age), blurred vision from hyperopia often becomes more apparent.

Presbyopia, also known as the “short arm syndrome,” is a term used to describe an eye in which the natural lens can no longer accommodate. Accommodation is the eye’s way of changing its focusing distance: the lens thickens, increasing its ability to focus close-up. At about the age of 40, the lens becomes less flexible and accommodation is gradually lost. It’s a normal process that everyone eventually experiences.

Most people first notice difficulty reading very fine print such as the phone book, a medicine bottle, or the stock market page. Print seems to have less contrast and the eyes become easily fatigued when reading a book or computer screen. Early on, holding reading material further away helps for many patients. But eventually, reading correction in the form of reading glasses, bifocals, or contact lenses is needed for close work. However, nearsighted people can simply take their glasses off because they see best close-up.

Astigmatism means that the cornea is oval like a rugby ball, instead of spherical like a football. Most astigmatic corneas have two curves – a steeper curve and a flatter curve. This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near. Astigmatism often occurs along with near-sightedness or far-sightedness.